Hydraulic motor system



June 26, 1956 w. A. RAY 2,751,753

HYDRAULIC MOTOR SYSTEM Filed Jan. 11, 1955 a a cawrea a/pcwr /7a,

A. Ll/YE INVENTOR,

ATTORN EYS.

HYDRAULIC MOTOR SYSTEM William A. Ray, North Hollywood, Calif., assiguor to General Controls (10., a corporation of California Application January 11, 1955-, Serial No. 481,110

12 Claims. (Cl. 60-52) This invention relates to a fluid pressure operated device for desirably positioning a load, and also to an electrical control system therefor.

in apparatus of this character, a small displacement pump operated by a motor supplies fluid under pressure to one side of a piston connected to the load for moving the piston in one direction. A valve operable to relieve the pressure on the piston permits the piston to return under the influence of a biasing force such as a spring, to an initial position.

Control apparatus for positioning the piston at any intermediate position has been heretofore provided. Such apparatus requires, of course, control not only of the energization f the pump motor, but also of the relief valve. For maintaining an intermediate position, the relief valve must be closed and the energization of the pump motor interrupted.

Dependin upon the direction of desired change in position therefrom, the relief valve is either opened or the pump motor engaged.

Accurate and quick control has been difiicult, if not impossible, in the prior control devices, due to several factors. One factor is coasting of the motor after it is deenergized. Another factor is delay time in the various relays usually employed in such control devices.

it is an object of this invention to overcome these difficulties, and provide an improved control apparatus whereby it is possible accurately and quickly to position the piston.

It is another object of this invention to incorporate a speed control for the motor to eliminate overtravel thereof. It is another object to obviate relays in the control apparatus, thereby eliminating the appurtenant delay time.

it is still another obiect of this invention to provide a control apparatus of this character in which a single parameter is availed of to achieve appropriate desirable control of the entire mechanism.

To accomplish the foregoing object-s, use is made of a saturable reactor having operating windings connected to the pump motor, and a saturating winding in series with an electromagnet for Operating the relief valve.

By increasing the current, the relief valve is first closed. The reactance of the saturable reactor diminishes and the motor begins operation. Upon further decrease of the reactance, the motor increases in speed.

A single current control achieves appropriate operation of the entire mechanism.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of one embodiment of the invention. For this purpose, there is shown a form in the drawing accompanying and forming part of the present specification. This form will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of this invention is best defined by the appended claims.

Referring to the drawing, the single figure is a diagrammatic view of apparatus incorporating the present inventiou.

A load (not shown) is connected to a piston stem 10. This piston stem projects traversely through the bottom wall of a fluid-tight casing 12. An appropriate sealing structure 11 cooperates with the stem 10 and the casing 12.

A hydraulic cylinder 13 extends upwardly from the bottom wall of the casing 12 about the stem 10. A piston 16 secured to the upper end of the piston stem 10 and appropriately cooperable with the inner annular wall of the cylinder 13 defines an upper space 14a and a lower space 14b.

A cover or plug 17 received in the upper end of the cylinder 13 closes the upper cylinder space 14a. A helical compression spring 18 surrounding the stem 10 in the lower space 14b has opposite ends engaging respectively the lower side of the piston 16 and the bottom surface of the casing 12 Within the cylinder 13. This spring urges the piston 16 upwardly.

The casing 12 is substantially filled with an appropriate hydraulic fluid to a level substantially above the cylinder 13. Fluid under pressure may be conducted to the upper cylinder space 1-'-la to move the piston 16 downwardly against increasing force of the spring 18.

The cornpression spring 18 returns the piston 16 to an upper position limited by an annular flange 17a of the cap 17 upon relieving the pressure in the piston space.

A pump structure 19 operated by a motor 20 within the casing 12 is provided for supplying fluid under pressure.

Rotation of the armature of motor 20 serves to operate the pump; for example, by aid of an eccentric 22 and crank arm 23 reciprocates a plunger 24 in a cylinder space 25 formed in a pump body 26. The fluid is admitted to the piston space 25 through an exteriorly opening port 27 in communication with the space 25 only when the plungor is retracted. The fluid from the space 25 is urged past a check valve structure 28 and thence through a passage 3% formed in a fitting 29. A conduit 21 establishes communication between the passage 30 and the upper cylinder space 14a, the ends of the conduit 21 being respectively fitted into an aperture 31 formed in the cover 17 and an enlarged end portion of the fitting passage 30.

In order to relieve the pressure in the piston space appropriately to affect the position of the piston 16, a conrollable relief passage 32 is provided.

This relief passage 32 is formed in the fitting 29 and intersects the passage 30 thereof. The relief passage 32 opens outwardly of the fitting 29 within an annular seat formed by a boss 33. The relief valve passage 32 is continuously in communication with the upper piston space 14a. Escape of fluid under pressure through relief passage 32 may be prevented by an armature closure 34 engaging the seat.

Upon operation of the motor 20, and providing the armature closure 34 is in valve closing position, fluid is urged under pressure to the cylinder space 14a, to move the piston 16 downwardly.

Upon movement of the armature closure 34 to unto its lower limited position, and with the relief passage 32 closed.

For controlling the armature closure 34,]an electromagnet structure 35 is provided. The armature closure 34 is pivotally movable about a knife. edge 36 formed at the end of an arm 37; A tension spring 38 biases the armature closure 34 toward a limited clockwise position corresponding to opening of the relief passage 32. The upper end of the armature closure 34 opposes a polararea formed at the end of a core 39 joined to the arm 37. An electromagnet coil 40 upon the core 39,

when energized, causes the armature closure 34 to move in a counter-clockwise direction against the force of the tension spring 38 to close the relief passage 32.

Leads 41 and 42 for the coil 40 are adapted to be connected to an appropriate source of direct current for selective operation of the electromagnet.

The motor 20 is controlled by the supply of energy to the electromagnet leads 41 and 42. For this purpose the motor winding 43 is connected to a source of alternating current through a pair of series connected windings 47 and 48 of a shell type saturable core reactor 49.

One motor lead 44, through a single pole switch, connects one terminal of the winding 43 to one main of a source of alternating current. Another lead 45 establishes a connection to the other main of the source, by way of a limit switch generally designated at 46 (to be hereinafter described) and the series connected reactor winding 47 and 48.

The direct current for the electromagnet passes through a saturating winding 51 wound upon the central leg of the core of the reactor 49. For this purpose, the saturating winding 51 is interposed in one of the electromagnet leads 42. v

In the absence of direct current, suficient to close the relief valve, the reactance. of the windings 47 and 48 is.

sufliciently high to prevent operation of the motor 20. Upon increase of the direct current through saturating winding 51 in an amount just corresponding to operation of the electromagnet to close the relief valve 32, the motor is yet not sutficiently energized to cause operation of pump '19. Upon increase in the direct current in a predetermined amount, the reactance of the saturating core reactor 49 is sufficiently reduced to cause operation of the motor 29 and the pump. Still further increase in the control current causes the motor to increase in speed.

Upon critical movement of the piston 16 corresponding to a lower limited position thereof, the limit switch 46 operates to interrupt the energizing circuit of the motor 20.

An arm 51 forming an element of the limit switch is angularly positioned in accordance withthe position of the stem 10. For this purpose an appropriate pin and slot connection is provided between the piston stem .10 and the arm 51. The arm 51 carries a movable contact '52 engageable with a relatively stationary contact 53. The relatively stationary contact 53 is mounted at the end of a flexible arm 54 connected to the motor winding 43. A flexible connection 55 is secured to a terminal 56 that is connected with the movable contact 52.

The flexible arm 54 permits the contacts 52 and 53 to engage each other and complete the circuit for the motor winding 43 for all positions of the mechanism except at thelower extreme position of the piston 16.

Conveniently the end 51a of the arm 51 may form an indicator for the mechanism. v

In the position shown, direct current is passed through the electromagnet leads 41 and 42 in an amount sufficient to close the relief passage 32 as by appropriate adjustment of variable resistance 57. The piston 16 has reached its lower extreme position, the limit switch 46 being open and theenergizing circuit for the motor 2% interrupted.

Fluid in the cylinder space 14a is trapped, since. the relief passage 32 is closed, and since the check valve 28 prevents return of fluid to the pump chamber 25.

If desired the control current to the electromagnet 35 may be reduced to a value just'suificicnt to keep the armature closure 34 in closed position. By careful con trol of the direct current the relief passage 32 can be opened for a time sufficientto permit upward movement of the piston 16 to an intermediate position. In such an intermediate position the limit switch 46 is closed; the motor 20, however, may not be sufficiently energized through reactance 49 to operate pump 20. The piston 16 may be moved in either direction either by increasing the control current in an amount sufficient to operate the motor 20, or it may be reduced again to open the relief passage 32. When it is desired to hold the piston 16 in an intermediate position the control current is maintained intermediate the critical values corresponding to operation of the electromagnet 35 and operation of the motor 20.

In the event of current failure the relief passage 32 is opened and the piston 16 returns to its upper limited posi tion corresponding to a safe condition of the load.

By carefully controlling the direct current the motor 2 can be caused to slow down prior to arrival of piston 16 to the desired intermediate or limited position. 7

By virtue of this feature of control the time required desirably to position the piston 16 can be shortened, overtravel of the motor 20 being largely eliminated.

By the aid of a simple rheostat control, operated manually or by an automatic programming mechanism, the hydraulic mechanism is quickly, easily and accurately positioned.

The inventor claims:

1. In a system of the character described: a movable load operator; electrically energizable motor means for moving the load operator; an electrically energizable device for rendering said energized motor means efiective; a saturable reactor in circuit with the motor means, and including a direct current coil; and means connecting said controlling device to said coil, for reducing the reactor impedance when said controlling device is energized.

2. In a system of the character described: a movable load operator; electrically energizable motor means for moving the load operator; an electrically energizable device for rendering said energized motor means effective; a saturable reactor in circuit with the motor means, and including a direct current coil; means connecting said controlling device to said coil, for reducing the reactor impedance when said controlling device is energized; and means for adjusting the current through said controlling device.

3. In a system of the character described: a movable load operator; electrically energizable motor means for moving the load operator; an electrically energizable device for rendering said energized motor means effective; a saturable reactor in circuit with the motor means, and including a direct current coil; means connecting said controlling device to said coil, for reducing the reactor impedance when said controlling device is energized; and

means for de-energizing said motor means upon a limit of for said first electrically energizable means, including'a' saturable core reactor;-second electrically energizable means for operating said controllable means; an energization circuit for said second electrically energizable means; and means for supplying a saturating current tov said saturable core reactor in proportion to the current supplied to said second electrically energizable means.

5. In apparatus for controlling the position of a'load:

a cylinder; a piston inthe cylinder; a pump for supplying fluid under pressuretothe cylinder; means forming a relief passage communicating with the cylinder; electrically operated valve means operable only upon sufficient electrical energization to close 12 e relief passage; a motor for operating the pump; means controlling the intensity of energization of said electrically operated valve means; an energization circuit for said motor including a saturable core reactor, the reactance of which determines the operation of said motor; and a saturating winding for said reactor and saturating said reactor in accordance with the intensity of energization of said electrically operated valve.

6. In apparatus for controlling the position of a load: a cylinder; a piston in the cylinder; a pump for supplying fluid under pressure to the cylinder; means forming a relief passage communicating with the cylinder; electrically operated valve means operable only upon sufficient electrical energization to close the relief passage; a motor for operating the pump; means controlling the intensity of energization of said electrically operated valve means; an energization circuit for said motor, including a saturable core reactor, the reactance of which determines the operation of said motor; and a saturating winding for said reactor in accordance with the intensity of energization of said electrically operated valve; said motor being operable only upon electrical energization of said electrically energizable valve in an amount more than suflicient to close said valve.

7. In apparatus for controlling the position of a load: a cylinder; a piston in the cylinder; a pump for supplying fluid under pressure to the cylinder; means forming a relief passage communicating with the cylinder; electrically operated valve means operable only upon sutficient electrical energization to close the relief passage; a motor for operating the pump; means controlling the intensity of energization of said electrically operated valve means; an energization circuit for said motor including a saturable core reactor, the reactance of which determines the operation of said motor; and a saturating winding for said reactor and saturating said reactor in accordance with the intensity of energization of said electrically operated valve; said energization circuit for said motor including a limit switch opened only upon sulficient movement of said piston in one direction.

8. In apparatus for controlling the position of a load: a cylinder; a piston in the cylinder; a pump for supplying fluid under pressure to the cylinder; a motor for operating the pump; an energization circuit for the motor, including a Winding of a saturable core reactor connected in series with the motor; means forming a relief passage communicating with the cylinder; an electromagnetically operated valve mechanism operable only upon sufficient energization to close the relief passage; an energization circuit for the mechanism, including in series, a saturating winding for said saturable core reactor; and means for controlling the intensity of energization of said energization circuit of said mechanism.

9. In apparatus for controlling the position of a load: a cylinder; a piston in the cylinder; a pump for supplying fluid under pressure to the cylinder; a motor for operating the pump; an energization circuit for the motor, in cluding a winding of a saturable core reactor connected in series with the motor; means forming a relief passage communicating with the cylinder; an electromagnetically operated valve mechanism operable only upon sufficient energization to close the relief passage; an energization circuit for the mechanism, including in series, a saturating winding for said saturable core reactor; and means for controlling the intensity of energization of said energization circuit of said mechanism; the reactance of said reactor permitting operation of said motor only upon a level of energization of said mechanism more than sufficient to close said relief valve.

10. In apparatus for controlling the position of a load: a cylinder; a piston in the cylinder; a pump for supplying fluid under pressure to the cylinder; a motor for operating the pump; means forming a relief passage cornmunicating with the cylinder; a normally open valve for controlling the relief passage; an electromagnet, operable only upon sufficient amount of energization, to close the valve; means for varying the intensity of energization through a range including the closing of the valve, in which the electromagnet closes the valve and opens the valve; an energization circuit for the motor; and circuit means operable upon an increase in the energization of said electromagnet for increasing the intensity of energization of the motor through a range including initial operation of said motor.

11. In apparatus for controlling the position of a load: a cylinder; a piston in the cylinder; a pump for supplying fluid under pressure to the cylinder; a motor foropcrating the pump; means forming a relief passage communicating with the cylinder; a normally open valve for controlling the relief passage; an electromagnet for closing the valve; means for varying the intensity of energization of the electromagnet through a range of values; the electromagnet closing the valve at an intermediate valve; an energization circuit for the motor; and circuit means for varying the intensity of energization of said motor through a range of values in accordance with the intensity of energization of said electromagnet.

12. In apparatus for controlling the position of a load: a cylinder; a piston in the cylinder; a pump for supplying fluid under pressure to the cylinder; a motor for operating the pump; means forming a relief passage communicating with the cylinder; a normally open valve for controlling the relief passage; an electromagnet for clos ing the valve; means for varying the intensity of energization of the electromagnet through a range of values; the electromagnet closing the valve at an intermediate valve; an energization circuit for the motor; and circuit means for varying the intensity of energization of said motor through a range of values in accordance with the intensity of energization of said electromagnet, the intermediate value at which the motor operates corresponding to a value of energization of the electromagnet in excess of the intermediate value at which said relief valve closes.

References Cited in the file of this patent UNITED STATES PATENTS 

